Polycondensation of naphthalene and its alkyl derivatives

Article abstract of DOI:10.1134/S1070427208120185

Polycondensation of naphthalene and its alkyl derivatives (stripping oil, 2,5-dimethylnaphthalene) in the presence of aluminum halides was performed. Under the action of an ultrasonic field on a benzene solution of naphthalene in the presence of the catalyst, intermolecular condensation and benzene addition are observed.

Full text of DOI:10.1134/S1070427208120185

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 12, pp. 2137–2140. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.V. Golounin, E.N. Marakushina, S.A. Khramenko, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 12,
pp. 2026–2029.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Polycondensation of Naphthalene and Its Alkyl Derivatives
A. V. Golounin, E. N. Marakushina, and S. A. Khramenko
Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia
Krasnoyarsk Branch, Russian Engineering Company, Krasnoyarsk, Russia
Received May 23, 2008
Abstract—Polycondensation of naphthalene and its alkyl derivatives (stripping oil, 2,5-dimethylnaphthalene)
in the presence of aluminum halides was performed. Under the action of an ultrasonic field on a benzene solution of
naphthalene in the presence of the catalyst, intermolecular condensation and benzene addition are observed.
DOI: 10.1134/S1070427208120185
The formation of tarry by-products from aromatic
hydrocarbons at elevated temperatures and in the course
of alkylation in the presence of catalysts has been de-
scribed in the literature [1, 2]. In some cases, tars can
act as target products, rather than as contaminating
components. In particular, this occurs in preparation of
a binder for composite anodes in aluminum produc-
tion. It seemed appropriate to examine the possibility
of transformation of naphthalene and its alkyl deriva-
tives into more complex products under the influence
of catalysts and to evaluate the degree of conversion.
To accelerate the condensation, we used ultrasonic acti-
vation instead of prolonged heating. Aluminum halides
were tested as catalysts. It should be noted that the ef-
fect of ultrasound on fused aromatic hydrocarbons is
poorly understood. It has been reported [3] that, under
cavitation treatment, naphthalene undergoes cleavage
with the formation of the simplest gaseous compounds.
gas chromatography–mass spectrometry (GC/MS) are
listed in Table 1.
We found that heating of naphthalene for 0.5 h at
1
80°C in the presence of 10% aluminum chloride does
Table 1. Composition of stripping oil before and after
ultrasonic treatment in the presence of 10% AlBr , 0.5 h
3
Reten-
tion time,
min
Content, %
Compound
before
after
treatment treatment
,2,3,4-Tetrahydro-naphthalene 9.461 5.6
1
Naphthalene
Isoquinoline
Quinoline
9.885
10.757
11.149
12.505
11.680
11.935
12.855
13.040
13.207
13.418
13.452
13.674
13.885
18.7
3.7
1.0
1.0
16.1
7.5
7.1
2.5
3.3
2.7
1.8
1.0
0.5
0.2
0.2
0.1
2.0
3.6
5
-Methylquinoline
1-Methylnaphthalene
2-Methylnaphthalene
2-Ethylnaphthalene
4.2
5.2
19.5
1
1
1
2
2
1
1
2
1
-Ethylnaphthalene
,5-Dimethylnaphthalene
,3-Dimethylnaphthalene
,7-Dimethylnaphthalene
,3-Dimethylnaphthalene
,4-Dimethylnaphthalene
,4,5-Trimethylnaphthalene 14.491
,3,6-Trimethylnaphthalene 14.852
,4,6-Trimethylnaphthalene 15.089
EXPERIMENTAL
Liquid stripping oil was prepared by distillation of
coal tar pitch; its boiling point is about 300°C. An ul-
trasonic source (UZDN-2T device, nominal power
4
00 W, generator working frequency 22 kHz) was im-
mersed in a vessel with stripping oil containing 10%
AlBr . In the process, the temperature of the mixture
3
Fluorene
-Ethylbiphenyl
15.52
19.51
8.4
8.9
increased to 200°C. After keeping for 30 min and cool-
ing to room temperature, the mixture solidified. To
remove aluminum bromide, the mixture was poured
over with water and boiled, after which it was ex-
tracted with benzene. After removing the solvent, we
obtained a viscous tar. The results of its analysis by
3
Dibenzofuran
Acenaphthylene
Acenaphthene
Benz[a]pyrene
Perylene
14.764
13.832
14.297
26.684
11.5
8.5
7.7
28.4
1.6
0.1
28.353 Σ 97.6
2
137

2
138
GOLOUNIN et al.
Table 2. Composition of the reaction mixture obtained after
60°C. In the process, the mixture was bubbled with
–
1
ultrasonic treatment of a benzene solution of naphthalene in
air for 30 min at a rate of 200 ml min . After the treat-
ment completion, water was added, the mixture was
shaken, the aqueous solution was separated, and the tar
precipitated on the beaker walls was washed out with
benzene and acetone. The organic solutions were com-
–
1
the presence of 10% AlBr
.5 h)
3
(air flow 200 ml min , 60°C,
0
Compound
MW Yield, %
Naphthalene
-Phenylacetic acid
128
136
230
284
210
204
206
208
7.7
18.7
0.8
bined, dried over CaCl , filtered, and vacuum-evaporated.
2
The yield was quantitative. To evaluate the contribu-
tion from benzene condensation to the tar formation,
we subjected a solution of aluminum bromide in ben-
zene to ultrasonic treatment. No significant amount of
tar was formed upon 30-min treatment. The results of
GC/MS analysis of the tar are listed in Table 2.
2
Hexadecanoic acid
Oleic acid
0.7
1
1
1
1
2
1
1
2
,4-Diphenylbutane
-Phenylnaphthalene
0.8
4.6
0.7
4.7
The tar composition was determined on an HP
6
890A gas chromatograph equipped with an HP 5972A
mass-selective detector, using NIST CSD database
275000 compounds). We used an HP-5MS quartz col-
,2-Dihydro-1-phenylnaphthalene
,2,3,4-Tetrahydro-1-phenylnaphthalene
-Phenylnaphthalene
(
umn, 30 m long, 0.25 mm i.d., coated with a 0.3-μm
layer of 5% diphenyl–95% dimethylsiloxane copolymer.
204
280
254
254
178
312
252
258
278
8.9
1.0
1.5
5.3
0.4
0.5
0.2
2.1
0.5
,7-Diphenylnaphthalene
Conditions of GC/MS analysis: initial column
temperature 70°C, 4 min; linear heating at a rate of
1
,2 -Binaphthyl
1
–1
,2 -Binaphthyl
100 deg min ; final temperature 300°C, 5 min; vapor-
izer temperature 280°C; sample volume 1 μl. The mass
spectra were recorded with electron impact ionization
Phenanthrene
,10-Diphenylphenanthrene
Perylene
9
(
70 eV). The scanning rate was 1 scan per second, and
the scanning range, 40–600 amu.
1
1
1
1
1
The organic compounds were identified by com-
parison of the experimental mass spectra with those
from the NIST CSD database using the ChemStation
standard system for GC/MS data processing. Poly-
cyclic aromatic hydrocarbons (PAHs) were analyzed in
the mode of selective detection of individual ions, with
identification by characteristic ions and retention
times, using solutions of reference substances.
1
9
,2 ,3 ,4 -Tetrahydro-1,2 -binaphthyl
1
1
,10-Dihydrobenz[1 , 2 ]-anthracene
Benz[j]fluoranthene
Benz[k]fluoranthene
Tetrahydro[k]fluoranthene
Benz[e]pyrene
252
252
256
252
252
258
260
0.1
0.3
0.7
0.1
2.4
0.1
0.3
According to the chromatogram, the stripping oil
contained (%) naphthalene 18.7, alkylated naphthale-
nes 45, dibenzofuran 11.5, acenaphthene 7.6, and fluo-
rene about 2. High-boiling carcinogenic compounds
were absent (Table 1).
Benz[a]pyrene
Tetrahydrobenz[a]pyrene
Octahydrobenz[a]pyrene
After the cavitation treatment, the oil composition
changed considerably: The amount of naphthalene and
methylnaphthalenes decreased, and di- and trimethyl-
naphthalenes virtually disappeared. At the same time,
the amount of 2-ethylnaphthalene and dibenzofuran
increased, which suggests their relative inertness under
the experimental conditions. The appearance of benz[a]-
pyrene in the reaction mixture points to the occurrence
of polycondensation. Apparently, benz[a]pyrene is
not chromatographically detectable changes. There-
fore, we performed a combined cavitation-catalytic
treatment of naphthalene. The procedure was as follows.
A glass beaker was charged with 1 g of naphtha-
lene and 20 ml of benzene, after which 0.1 g of AlBr3
was added. A plate-type emitter was immersed, and
the UZDN-2T device was switched on. The tempera-
ture increased in the course of the treatment from 20 to
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POLYCONDENSATION OF NAPHTHALENE AND ITS ALKYL DERIVATIVES
2139
tified using the database on polycyclic compounds are
listed in Table 2.
Indeed, heating of a benzene solution of naphtha-
lene in the presence of AlBr at 60°C for 0.5 h under
3
the action of cavitation leads to formation, along with
other substances, of benz[a]pyrene and its hydrogen-
ated analogs: tetrahydro- and octahydrobenz[a]pyrenes.
The occurrence of this reaction pathway is also con-
firmed by the detection of 1,4-diphenylbutane among
reaction products.
At the same time, it should be noted that methy-
lated naphthalenes losing methyl substituents under the
conditions of acid catalysis can also be precursors of
benz[a]pyrene. To evaluate the possibility of this
route, we heated 2,5-dimethylnaphthalene with 10%
aluminum chloride at 180°C for 0.5 h. By liquid chro-
matography, we detected among reaction products ace-
naphthene, 2-methylnaphthalene, benz[a]pyrene, and
dibenz[a,h]anthracene (40.5, 28.1, 5.8, and 1.8%, re-
spectively).
Scheme 1.
formed by a sequence of reactions involving naphtha-
lene (Scheme 1).
According to Scheme 1, for the formation of benz-
[
a]pyrene to be formed, naphthalene should add a frag-
Along with undergoing disproportionation and
condensation, naphthalene also reacts with benzene to
form 1- and 2-phenylnaphthalenes, 1,2- and 1,7-
diphenylnaphthalenes, and their hydrogenation prod-
ucts. Also, naphthalene undergoes self-condensation to
form dinaphthyl and perylene. The formation of the
above products can be described by Scheme 2 involv-
ing radical cations. According to Scheme 2, the reac-
tion mixture should also contain dihydro- and tetrahy-
dro-1-phenylnaphthalenes, which were, indeed, detected
(Table 2). The formation of carboxylic acids (2-phenyl-
acetic, hexadecanoic, oleic) is attributable to the pres-
ence of air in the reaction medium.
ment consisting of phenyl residue and a radical with
four carbon atoms. Such a fragment can be formed
after hydrogenation of naphthalene to dihydronaphtha-
lene or tetralin. The ring opening in these compounds
will lead to formation of fragments required for “as-
sembling” benz[a]pyrene.
If the naphthalene transformation follows this pat-
tern, its polycondensation should lead to formation of
tetrahydrobenz[a]pyrene and benz[a]pyrene. Accord-
ing to the chromatogram, the naphthalene tar contains
more than 50 substances. The major components iden-
Scheme 2.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 12 2008

2
140
GOLOUNIN et al.
CONCLUSIONS
REFERENCES
1
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(
1) Naphthalene and its methyl derivatives trans-
form in the course of acid catalysis of the polyconden-
sation into a complex mixture of products, some of
which are carcinogenic (e.g., benz[a]pyrene).
1
949.
2
3
. Olah, G.A., Friedel–Crafts and Related Reactions, 1963,
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(
2) Ultrasonic treatment of a solution of naph-
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numerous high-molecular-weight polyaromatic de-
rivatives.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 12 2008